Saving the galaxy from mecha-chtulu is grimdark and emo now? Yes, sacrifices have to be made. It,s a damn Reaper invasion, a consequence-light ending (however how hard to acheive) would clash with the story.
Le me be more specific. Take ME2 and the Suicide Mission. Much touted in the marketing and by the devs, this is the mission that you prepare for all game long. Stop the Collectors, or die trying, and as the name says it's considered pure suicide. Yet, if you do all the loyalty missions and choose with a modicum of intelligence, you can easily get out with 0 casualties; in fact, any consequence for this so-called Suicide Mission is entirely in the player's hand. The only way to ''fail'' is to either rush through the game or to make more or less explicitely bad decisions. The Bad Ending is pretty much only attainable if you do it on purpose. This clashes hard with the fact that it's supposed to be a damn suicide mission. It's supposed to demand sacrifices. Yet you can just waltz in and kill everybody without suffering any losses. Yes, I guess it was ''awesome'', but it also didn't fit the game and was anticlimatic to a degree.
Fast forward to ME3 (by the way, we still don't know the intricate details of the endings, only the outlines, so I suggest we give it time; anyway). Reaper invasion, Sword holds the line while the Hammer helps Shepard blaze a way to the MacGuffin du jour. Said Macuffin is used, Reapers are defeated... but at a terrible price, as they should be. Imagine that the endings are generally bad, save one where there are much less consequences. What's the point of the other endings then? It will be like in ME2, you have an optimal, Good Ending, then OK endings, then a Bad Ending. In the leaks I simply see different endings, no Bad One and go Good One, or at least much less than in ME2. And I much prefer it that way. Let me choose the ending (and yes, they do change the fate of the galaxy a fair bit), don,t choose it for me depending on how much time I played the game, don't put an ideal ending next to which the rest are sub-par and feel incomplete.
That said, I think they could have made it a bit less extreme. A good example is Planescape:Torment
PLANESCAPE TORMENT SPOILERS BELOW THIS IS AN AWESOME GAME DON'T SPOIL YOURSELF DON'T SPOIL YOURSELF DON'T SPOIL YOURSELF ALRIGHT? GOOD READ ON THEN
The gist of the ending doesn't change; the Nameless One has vainquished his mortality and must now purge his sins in the Blood War. The ending changes 1) how he does it (kills himself, wills himself out of existence, defeats his mortality, merges with his mortality) and 2) if he can say farewell to his companions. It really fits the game's tragic nature, since it was clear that the Nameless One was doomed if you followed the in-game hints a bit; his previous incarnations did too much evil. But you can still have a very fulfilling ending bying farewell to all the people who accompanied you on your journey. ME3 could have used this (maybe it has it, who knows); Shepard dies, but he is surrounded by his crew and can say farewell (have the Normandy crash with no medical equipment nearby, I don't know, just throwing ideas out there) to all of them before expiring. And while this can be cliche, for having experienced that myself it can be extremely powerful.
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So yeah, I don't find the endings ''emo'' (which is a term so overused it doesn't mean anything anymore for that matter). I would change one thing about it, that's it that's all.